Search for neutral MSSM Higgs bosons decaying to mu(+) mu(-) in pp collisions at root s=7 and 8 TeV

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DOI: 10.1016/j.physletb.2015.11.042

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by Elsevier. All rights reserved.

DIRETORIA DE TRATAMENTO DA INFORMAÇÃO

Cidade Universitária Zeferino Vaz Barão Geraldo

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Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Search

for

neutral

MSSM

Higgs

bosons

decaying

to

μ

+

μ

−

in

pp

collisions

at

√

s

=

7 and 8 TeV

.

CMS

Collaboration



CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received6August2015

Receivedinrevisedform2November2015 Accepted10November2015

Availableonline23November2015 Editor:M.Doser Keywords: CMS Physics Higgs MSSM Dimuons

A searchfor neutralHiggs bosonspredicted inthe minimalsupersymmetricstandard model (MSSM) for

μ

+

μ

−decaychannelsispresented.Theanalysisusesdata collectedbytheCMSexperimentatthe LHCinproton–protoncollisionsatcentre-of-massenergiesof7and8 TeV,correspondingtointegrated luminositiesof5.1and19.3 fb−1,respectively.ThesearchissensitivetoHiggsbosonsproducedeither throughthegluonfusionprocessorinassociationwithabb quarkpair.Nostatisticallysignificantexcess isobservedinthe

μ

+

μ

−massspectrum.Resultsareinterpretedintheframeworkofseveralbenchmark scenarios,andthedataareusedtosetanupperlimitontheMSSMparametertanβasafunctionofthe massofthepseudoscalarAbosonintherangefrom115to300 GeV.Modelindependentupperlimitsare givenfortheproductofthecrosssectionandbranchingfractionforgluonfusionandbquarkassociated productionat√s=8 TeV.Theyarethemoststringentlimitsobtainedtodateinthischannel.

©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

The predictions of the standard model (SM) [1–7] of funda-mental interactions have been confirmed by a large number of experimentalmeasurements.Theobservationofanewbosonwith amassof125 GeVandpropertiescompatiblewiththoseoftheSM Higgs boson [8–10] confirms the mechanism of the electroweak symmetrybreaking (EWSB).Despitethe successofthistheory in describingthe phenomenology of particlephysics atpresent col-lider energies, the mass of the Higgs boson in the SM is not protectedagainstquadraticallydivergentquantum-loopcorrections athighenergy. Supersymmetry(SUSY) [11,12]is one exampleof alternativemodelsthataddressthisproblem.InSUSY,such diver-gences are cancelledby introducing a symmetry between funda-mentalbosonsandfermions.

Theminimal supersymmetricextensionofthe standardmodel (MSSM)[13,14]predictstheexistenceoftwoHiggsdoubletfields. Onedoublet couples to up-typeandone to down-typefermions. AfterEWSB, fivephysical Higgsbosons remain: a CP-oddneutral scalarA,two chargedscalarsH±,andtwoCP-evenneutralscalar particlesh and H.Theneutralbosons h,A,andH,willbe gener-icallyreferredto as

φ

collectivelyinthispaper,unlessdifferently specified.

 _{E-mailaddress:cms-publication-committee-chair@cern.ch.}

Atlowestorderinperturbationtheory,theHiggssectorinthe MSSMcanbedescribed intermsoftwofreeparameters:mA,the

massoftheneutralpseudoscalarA,andtan

β

,theratioofthe vac-uum expectationvaluesofthetwoHiggsdoublets.Themassesof the other fourHiggs bosons can be expressed in terms of these twoparametersandothermeasuredquantities,suchasthemasses mW and mZ of the W and Z bosons, respectively. In particular,

themassesoftheneutralMSSMscalarHiggsbosonsH andh are given[13]by mH,h

=



1 2



m2_A

+

m2_Z

±



m2_A

+

m2_Z



2

−

4m2_Am2_Zcos22

β



1/2



1/2

.

(1)

The Aand H bosonsare degenerate inmass above140 GeV and forsmall cos

β

(large tan

β

) values.Thisexpression alsoprovides an upperbound onthemassofthelightscalarHiggsboson, cor-responding to mh

≤

mZ

|

cos 2

β

|

. The value can become as large

as mh

≈

135 GeV once radiative corrections are taken into

ac-count[15].

The main production mechanisms for the three neutral

φ

bosons at theLHC are the associated productionwith bb quarks (AP), given atthe leading order by the Feynman diagram shown inFig. 1(top),andthegluon fusion(GF)process,showninFig. 1 (bottom)[16–18].TheGFprocesswithvirtualtorbquarksinthe http://dx.doi.org/10.1016/j.physletb.2015.11.042

0370-2693/©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

Fig. 1. Leading-orderdiagramsforthemainproductionprocessesofMSSMHiggs bosonsattheLHC(top)inassociationwith bb productionand(bottom)through gluonfusion.

loop isdominantatsmallandmoderatevalues oftan

β

. Atlarge tan

β

thecouplingof

φ

todown-typequarksisenhancedrelative to theSM [19] andtheAP process becomes dominant. Similarly, thecouplingofthe

φ

bosontochargedleptonsisalsoenhancedat largetan

β

.

This paper reports on a search for the MSSM neutral Higgs bosons produced eitherby the APorGFmechanisms, wherethe Higgs bosons decay via

φ

→

μ

+

μ

−. The analysis is sensitive to allthe threebosons, h,H,andAinthe massrangebetween115 and300 GeV. The search is performedby theCMS collaboration usingdatarecordedin ppcollisions attheLHC,corresponding to anintegratedluminosityof5.1 fb−1at

√

s

=

7 TeV and19.3 fb−1at

√

s

=

8 TeV.The commonexperimental signatureofthetwo pro-cessesisapairofoppositelychargedmuonswithhightransverse momentum(pT)andasmallimbalanceofpT intheevent.TheAP

processischaracterizedbythepresenceofadditionaljets originat-ingfrombquarks(bjets),whereastheeventswithonlyjetsfrom light quarksorgluonsare sensitive tothe GFproduction mecha-nism.Thepresenceofasignalwouldbecharacterizedbyanexcess ofeventsoverthebackgroundinthe dimuoninvariantmass cor-respondingtothe

φ

massvalue.

Although the product of the cross section and the branching fractionforthe

μ

+

μ

−channelisafactor103 _{smallerthanforthe}

corresponding

τ

+

τ

−finalstate,themuonpaircanbefully recon-structed,andtheinvariantmasspreciselymeasuredby exploiting the excellent muon momentum resolution of the CMS detector. SearchesfortheMSSMHiggsbosonshavebeenperformedatLHC bytheLHCbexperimentinthe

τ

+

τ

−finalstateatlarge pseudora-pidityvalues[20],theATLAS experimentinthe

μ

+

μ

− and

τ

+

τ

−

channels [21,22], andby the CMSexperiment in the

τ

+

τ

− [23] andbb[24,25]finalstates.LimitsontheexistenceofMSSMHiggs bosonswerealsodeterminedatTevatron[26–29]andatLEP[30].

Traditionally,searchesforMSSMHiggsbosonsarepresentedin the context ofbenchmark scenarios that describe the mass rela-tion among the three neutral MSSM Higgs bosons, their widths, andcrosssections.Eachscenarioassignswelldefinedvaluestothe relevantparametersoftheMSSM,exceptmA andtan

β

,whichare

left free to vary. The mmax

h benchmark scenario [19,31] provides

mh valuesaslarge as135 GeV, andtheweakestboundsontan

β

forfixedvaluesofthetopquarkmass.Forthisreason,ithasbeen usedinmostofthepreviouslyquotedanalyses topresentthe re-sultsfromMSSMHiggsbosonsearches.However,withintheMSSM thenewly discoveredstate withamassof125 GeVcanbe inter-pretedasthelightCP-evenHiggsboson,h[32].Inthiscase,alarge

partofthemA– tan

β

parameterspaceisexcludedwithinthemmax_h

scenario,andnewbenchmarkswerethereforeproposed inwhich theMSSMparametersareadjustedtohavemhintheinterval122

to 128 GeV,but withawider range oftan

β

andmA values[19,

31,32]. To do this, the mmax

h scenario was reformulated in two

versions,mmod_h + andmmod_h −, corresponding todifferent valuesof thetopsquarkmixingparameter.Otherrecentlyproposed scenar-ios[31] arethelight topsquark(lightstop)model,whichresults inamodifiedGFrate,andthelighttauslepton(lightstau)model, which yields a modified h

→

γ γ

branching fraction. Such mod-elsareexpectedmainlytoaffecttheHiggsbosonproductioncross sectionandnotthekinematicpropertiesoftheevents.A listofthe parametersofthevariousscenarioscanbefoundinRef. [23].The results presentedin thispaperare obtainedin theframework of theMSSMmmod_h +scenario.Comparisonsarealsomadewithother benchmarks.

2. TheCMSdetectorandeventreconstruction

The central feature of the CMS apparatus is a superconduct-ing solenoidof6 m internal diameter,providing amagneticfield of3.8 T.Withinthe solenoidvolumeare asiliconpixel andstrip tracker,aleadtungstatecrystalelectromagneticcalorimeter(ECAL), andabrassandscintillatorhadron calorimeter(HCAL),each com-prised ofa barrelandtwo endcapsections.Muonsaremeasured ingas-ionizationdetectorsembeddedinthesteelflux-returnyoke outside the solenoid. Forward calorimetry extends the coverage providedby thebarrelandendcapdetectorsuptopseudorapidity

|

η

|

<

5.AdetaileddescriptionoftheCMSdetector,togetherwitha definitionofthecoordinatesystemandkinematicvariables,canbe found inRef.[33].TheCMSofflineeventreconstruction createsa globaleventdescriptionusingtheparticleflow(PF)technique[34]. The PF eventreconstruction attemptsto reconstruct andidentify eachparticlewithanoptimizedcombinationofallsubdetector in-formation. The missing pT vector is definedasthe projection on

the planeperpendicular tothebeams ofthenegative vectorsum ofthemomentaofallreconstructedparticlesinanevent.Its mag-nitudeisreferredtoasEmiss

T .

An average of 9 and 21 pp collisions take place in any LHC bunch crossing, respectivelyat7 and8 TeV, becauseofthe large luminosity ofthemachineandthesizeofthetotalinelasticcross section. These overlapping events (pileup) are characterized by small-pT tracks, compared to the particles produced in a

φ

→

μ

+

μ

−event,andtheirpresencecandegradethedetector capabil-itytoreconstructtheobjectsrelevantforthisanalysis.Theprimary vertexischosen fromall reconstructedinteractionverticesasthe one withthe largestsumin thesquaresof the pT of the

associ-atedtracks.Thechargedtracksoriginatingfromanothervertexare thenremoved.

Offline jet reconstruction is performedusing the anti-kT

clus-teringalgorithm [35,36]witha distanceparameterof0.5.The jet momentum isdefinedby thevectorialsumofallthe PFparticles momenta in thejet, andfound in simulation tobe within 5% to 10%ofthetruehadron-levelmomentum,withsome pT and

η

de-pendence.Extraenergycomingfrompileupinteractionsaffectsthe momentummeasurement.Correctionstothemeasuredjetenergy arethereforeapplied.Theyarederivedfromeventsimulation,and confirmedwithin-situmeasurementsusingenergybalanceindijet andZ/photon

+

jetevents[37].

Muonsaremeasuredinthepseudorapidityrange

|

η

|

<

2

.

4, us-ingdetectionplanesbasedonthreetechnologies:drifttubes, cath-odestripchambers,andresistive-platechambers.Matchingmuons totracksmeasuredinthesilicontrackerprovidesrelativepT

Table 1

ThemAandtanβvaluesusedtogeneratesignalsamples.

mA(GeV) mAstep (GeV) tanβ tanβstep

115–200 5 5–55 5

200–300 25 5–55 5

300–500 50 5–55 5

andbetterthan6%intheendcaps.The pT resolutioninthebarrel

isbetterthan10%formuonswithpT upto1 TeV[38].

3. Simulatedsamples

Simulatedsamplesareused tomodel thesignal andto deter-minetheefficiencyofthesignalselection.Backgroundsamplesare alsosimulatedtooptimizetheselectioncriteria.Thenormalization anddistributionofthebackgroundeventsaremeasuredfromdata. Thesignal samples aregenerated usingthe MonteCarlo(MC) eventgenerator pythia 6.424[39]forawiderangeofmAandtan

β

values,aslistedinTable 1,fortheAPandtheGFproduction mech-anisms.The

φ

production cross sectionsandtheir corresponding uncertaintiesareprovidedbytheLHCHiggsCrossSectionWorking Group[16–18].ThecrosssectionsfortheGFprocessinthemmax_h scenario are obtained using the HIGLU program [40,41], based on next-to-leadingorder (NLO) quantum chromodynamics (QCD) calculations.The sushi program[42] isusedfortheother bench-marks.FortheAPprocess,thefour-flavorNLOQCDcalculation[43, 44]andthefive-flavor next-to-next-to-leadingorder(NNLO) QCD calculationareimplementedin bbh@nnlo[45]andcombined us-ingthe Santandermatchingscheme[46].TheHiggsYukawa cou-plings computed with the feynhiggs program [47] are used in the calculations. The decay branching fractions to muons in the different benchmark scenarios are obtained with feynhiggs and hdecay[48].Furtherdetailson signalgeneration canbe foundin Refs.[16–18].

Thevalues ofmh predicted by feynhiggs differtypically by a

few GeV from those computed with pythia. The invariant mass spectrumof the h boson istherefore shifted tomatch the feyn-higgsprediction.The smalldifference between pythia and feyn-higgs in assessing the width of the h boson is of the order of 100 MeV, and therefore neglected, since the experimental mass resolution is at least one order of magnitude larger. The pythia parametersusedtosimulatethesignalarethoseforthemmax

h

sce-nario.SinceforagivensetofmA andtan

β

values,thekinematic

propertiesofthefinalstate arethesameforallthescenarios,the simulatedsamplesbasedonthemmax

h benchmarkarealsousedto

checkthevalidityoftheothermodels.Furtherdetailsonthis pro-cedure and the related systematic uncertainties are discussed in Section7.

Themain source ofbackground forthe

φ

production and de-cay to

μ

+

μ

− isDrell–Yan muon-pairproduction, qq

¯

→

Z

/

γ

∗

→

μ

+

μ

−.Anotherbackgroundisfromoppositelychargedmuonpairs produced indecays of top quarks in t

¯

t production. Theseevents aresimulatedusingthe MadGraph 5.1[49]generator.Other back-groundprocessessuchasW±W∓,W±Z,andZZ aregeneratedwith pythia. The MC samples also includesimulated pileup events to reproducetheoverlappingppinteractions presentinthedata.All generated events are processed through a detailedsimulation of theCMSdetectorbasedon Geant4[50]andarereconstructedwith thesamealgorithmsusedfordata.

4. Eventselection

The experimental signature of the MSSM Higgs bosons decay consideredin thisanalysisisa pairofoppositely chargedmuons

Table 2

Eventselection:thecriterialistedintheupperpartofthetablearecommontothe C1andC2categories,thatarethenmutuallyexclusive.

Common selection

Single muon trigger pT>24 GeV+isolation+ |η| <2.1

Event primary vertex |zPV| <24 cm

Muon selection 2 opposite-charged muons,

pT>24 GeV,|η| <2.1,

track quality cuts,

|dxy| <0.02 cm,|dz| <0.1 cm,

angular matching with trigger, isolation Emiss T E miss T <35 GeV Category C1

b tag 1 or 2 b-tagged jets,

pjetT >20 GeV,|ηjet| <2.4

Category C2

No b tag Events with no b-tagged jets

with high pT. The invariant mass of the paircorresponds to the

massofthe

φ

bosonwithintheexperimentalresolution.Moreover, theprocessischaracterizedbyasmallEmiss_T intheevent.Ifthe

φ

bosonisproducedinassociationwithabb pair,thepresenceofat leastonebquarkjetisexpected.

Thedetailsoftheeventselectionarelistedbelow,and summa-rizedinTable 2.Theeventsareselectedusingasingle-muon trig-ger,whichrequiresatleastone isolated muonwith pT

>

24 GeV

inthepseudorapidityrange

|

η

|

<

2

.

1.Thedistanceoftheprimary vertex along the z axisfrom the nominalcentre of the detector must be

|

zPV

|

<

24 cm. Muon candidates are reconstructed and

identifiedusingboththeinner trackerandthemuondetector in-formation.Theselectedeventsmusthaveatleasttwo oppositely-chargedmuoncandidates,each withpT

>

25 GeV.Ineventswith

more than two muon candidates, the two withopposite charges andthe highest pT are retained.The

η

of both muoncandidates

ischosen tomatchthetriggeracceptance.Eachmuontrackmust haveatleastonehitinthepixeldetector,morethanfiveoreight layers with hits inthe tracker, respectively, for the 8 and7 TeV data and a directional matching to hits in at leasttwo different muondetectorplanes.Inadditiontheglobalfittothehitsofthe muon candidate must include at least one hit in the muon de-tector. The

χ

2

_/

_{dof of the global fit of the muon track must be}

smallerthan 10.Theserequirementsensure agoodmeasurement ofthemomentum,andsignificantlyreducetheamountofhadronic punch-through background [38]. Toreject cosmic ray muons, the transverseandlongitudinalimpactparametersofeachmuontrack mustsatisfy the requirements

|

dxy

|

<

0

.

02 cm and

|

dz

|

<

0

.

1 cm,

respectively. Both parameters are definedrelative to the primary vertex.Toensurethatthetriggermuoncandidateiswell-matched to the reconstructed muon track, at least one of the two muon tracks isrequiredto matchthe directionofthetrigger candidate within a cone

R

=

0

.

2, where

R

=

√

[

b

](

η

)

2

+ (

ϕ

)

2 is the distancebetweenthemuontrackandthetriggercandidate direc-tioninthe

η

–

ϕ

plane,with

ϕ

beingtheazimuthalanglemeasured inradians. Bothreconstructed muoncandidatesmust fulfill isola-tion criteria. A muon isolation variable is constructed using the scalar sum of the pT of all PF particles, except the muon,

re-constructed within a cone

R

=

0

.

4 around the muon direction. Acorrection isapplied to accountforthe possiblecontamination fromneutralparticlesarising frompileup interactions.Amuon is acceptedifthevalueofthecorrectedisolationvariableislessthan 12%ofthemuonpT.

A selection based on Emiss_T provides good separation between signal eventsand t

¯

t background,in thecaseof leptonic decayof

Fig. 2. TheEmiss

T distributionforeventswithareconstructeddimuoninvariantmass

mμ+μ−>60 GeV indataandinsimulatedeventsat√s=7 (top)and√s=8 TeV (bottom).TheexpectedcontributionisalsoshownforasignalatmA=150 GeV and

tanβ=30.

the W boson from top decay. The Emiss_T distributions for events collectedat

√

s

=

7 and8 TeVareshowninFig. 2foreventswith areconstructedmuon pairwithinvariant mass_mμ+_μ−

>

60 GeV. The background contributions from SM processes are superim-posed. For illustration, the expected distribution for signal pro-cesses is also shown formA

=

150 GeV and tan

β

=

30. Studies

performedusing the simulation show that the Emiss_T distribution forsignal eventsdoesnot vary significantly fordifferentmA and

tan

β

assumptions,andindicatethat theselection Emiss_T

<

35 GeV provideshighestsensitivityforsignalatbothcentre-of-mass ener-gies.

Thereconstructedjetsarerequiredtohavetransversemomenta pjet_T

>

20 GeV within the range

|

η

|

<

2

.

4. A multivariate analysis techniqueisusedtoremovejetsfrompileupinteractions[51]. Tag-gingof bquarks injetsrelieson thecombined secondary-vertex discriminator [52],based on the reconstruction of the secondary vertex from weakly decaying b hadrons. The discriminant bdisc

isconstructedfromtracks andsecondary vertexinformation,and helpsto distinguishjets containing b,c,or light-flavourhadrons. Jetswithanassociatedbdisc

>

0

.

679 areconsideredtobebtagged.

Thisvaluerepresentsagoodcompromisebetweenefficiencytotag bjetsinsignaleventsfromAP(

≈

80%)andmistaggingprobability forlight-quarkjets(

≈

1%).Fig. 3showsthedistributionofbdisc in

Fig. 3. Thedistributionofthebtaggingdiscriminant,bdisc,foreventsthatsatisfythe

selectionEmiss

T <35 GeV indatacollectedat

√

s=7 (top)and√s=8 TeV (bottom). Foreachevent,thelargestvalueofbdiscisselected.

eventsthat satisfy theselection Emiss

T

<

35 GeV,forthedata

col-lected inthetwobeamenergies.Foreachevent,thelargestvalue of bdisc is selected.The distribution ofsignal eventsfrom theAP

process for mA

=

150 GeV and tan

β

=

30 is superimposed. Jets

originated from b quark fragmentation tend to be emitted more forwardinsignaleventsthan fort

¯

t,thus resultinginalower ob-served b-jetmultiplicity.Forthisreasonthet

¯

t backgroundis fur-thersuppressedbyrejecting eventswithmorethantwob-tagged jets, withoutsignificantly affectingtheselectionefficiencyfor sig-nal.

Theeventsaresplitintotwomutually-exclusivecategories.The first category(C1)contains eventswithatleastonejet identified asoriginatedfromb-quarkfragmentation(btagged),andprovides highest sensitivity to AP production channel. Events that do not containb-taggedjetsare assignedtocategory2(C2),andprovide sensitivityto GFproduction.The dimuoninvariant mass distribu-tions for the C1 and C2 categories are shown in Fig. 4 for data and simulated events for both centre-of-mass energies. The dis-tributions expected forMSSM Higgs bosons with mA

=

150 GeV

and tan

β

=

30, derived from the mmod_h + scenario are also given forcomparison.Adoublepeakstructurearound125and150 GeV appears intheC2category,duetothehboson andA

+

H bosons, respectively.The lowerpeakisnot visibleinC1,astheh produc-tionissuppressedintheAPmechanismrelativetotheGFprocess.

Fig. 4. ThedimuoninvariantmassdistributionforeventsthatbelongtoC1(upperleft)andC2category(upperright),fordataandsimulatedeventsat√s=7 TeV.The correspondingquantitiesareshownfor√s=8 TeV (lowerleftandlowerright).Theexpectedcontributionstosignalassumingthemmodh +scenarioformA=150 GeV and

tanβ=30 aredisplayedforcomparison.

5. Signalselectionefficiency

WhilethecalculationsfortheMSSMcross sectionsperformed inthenarrow-widthapproximationrefertotheon-shellHiggs bo-son production,at large values of mA and tan

β

the convolution

ofthe larger intrinsicsignal widths withthe parton distribution functions(PDF)resultsinanon-negligiblefractionofsignalevents producedsignificantlyoff-shell.Eventswithinvariantmass signifi-cantlysmallerthanitsnominalvaluehavealower reconstruction efficiency than those produced near the mass peak. For consis-tency, we define signal efficiency as the probability for a signal eventwiththegeneratedinvariantmassclosetoitsnominalvalue to be reconstructed and pass all selection requirements of this analysis.Theclosenessisdefinedusingawindowofsizeequalto 3timesthe intrinsicsignal width(anuncertaintyassociatedwith thisdefinitionis evaluated usinga windowof 5times its width, asdiscussedinSection7).Withthisdefinition,theproductofthe MSSMHiggsbosonproductioncrosssection,luminosityandsignal efficiencyprovidesthenormalizationfortheHiggsbosonproduced near on-shell. The full predicted rate of signal events also con-tains an additional off-shell contribution, which varies with mA

andtan

β

andislessthan 5% formA

<

250 GeV and tan

β <

15,

andcanbeaslargeas15%formA

=

300 GeV andtan

β

=

30.

Additional corrections are applied to the signal efficiency to takeintoaccount differencesbetweendataandsimulationinthe muon trigger, reconstruction, and isolation efficiencies. A

correc-tionisalsoappliedtoaccountforknowndata-simulation discrep-ancies inthe btaggingefficiencyandmistaggingprobability.The correctionsaresummarizedby aweight factor,whichisassigned toeach signal event.The averageoftheweight factorscomputed overalltheeventsisveryclosetoone,reflectingthefactthatthe simulationdescribesthedatawithgoodaccuracy.

Fig. 5 showsthe signal efficiencyat

√

s

=

8 TeV for AP (top) andGF(bottom)processaftercombiningthetwoeventcategories C1andC2.Theefficienciesat

√

s

=

7 TeV aresimilar.Thebandin thefigurerepresentsthevariationoftheefficiencyduetothe lim-itedstatistics ofthesamplesused.TherelativeamountofAPand GFevents inthe two eventcategoriesvarieswithmA and tan

β

,

since the production crosssections ofthe two processes depend ontheseparameters.Forexample,inthecasemA

=

150 GeV and

tan

β

=

30, more than 90% of the signal events in C1 would be fromAPproduction,andabout60%inC2.FormA

=

150 GeV and

tan

β

=

5,wherethe GFcontribution becomesmore relevant,the contentofAPeventswouldbe60%inC1andonly15%inC2. 6. Fitprocedure

TheproceduredescribedbelowisappliedseparatelytoC1and C2 events. The event selection criteria are applied to the simu-latedsamples listedin Table 1. Foreach sample, andforeach of the three

φ

bosons, theinvariant massdistribution ofthe events thatpasstheeventselectionisapproximatedwithaBreit–Wigner

Fig. 5. SignalefficiencyfortheAPprocessat√s=8 TeV,shownseparatelyforthethreeφbosontypes,(upperleft)h,(uppercentre)H,and(upperright)A,asafunction ofmA.ThecorrespondingefficiencyfortheGFproductionprocessisshowninthelowerrow.ThecontributionsfromthetwoeventcategoriesC1andC2arecombined.

Theresultsareintegratedovertanβ,sincetheefficiencydoesnotstronglydependonthisquantity.Thebandshowsthechangeinefficiencyduetothelimitednumberof simulatedevents.

functionconvolvedwithaGaussian,thataccountsfordetector res-olution. This analyticalexpression provides a good description of thesignal shapeforall themA andtan

β

values.The three

func-tionsaredenotedFh,FH,andFA,andcontainthemassandwidth

oftheBreit–WignerandthewidthoftheGaussianasfree param-eters.ThefunctionFsigrepresentstheexpectedsignalyield,andit

isalinearcombinationofthethreefunctionsdescribedabove:

Fsig

=

whFh

+

wHFH

+

wAFA

,

(2)

wherewh,wH,andwA,arethenumberofeventscontainingh,H,

andAbosons,respectively, calculatedaccordingtotheir expected productioncrosssections.Anexampleofthisprocedureisshown inFig. 6(top)formA

=

150 GeV and tan

β

=

30.Thehighestpeak

represents the superposition of the contributions from H and A bosons,thatinthiscasearealmostdegenerateinmass.

Since the Drell–Yan muon pair production is the dominant backgroundprocess,itismodeledbyaBreit–Wignerfunctionplus aphoton-exchangeterm,whichisproportionalto1

/

m2_μ+_μ−.

Defin-ingm

=

_mμ+_μ−,thefunctionFbkg becomes:

Fbkg

=

eλm

⎡

⎣

fZ N₁norm 1

(

m

−

mZ

)

2

+

 2 Z 4

+

(

1

−

fZ

)

Nnorm₂ 1 m2

⎤

⎦ ,

(3)

whereeλm describestheeffects ofthePDF, andthe Nnorm_i terms correspond to the integral ofthe corresponding functionsin the chosenmassrange.Thequantity fZrepresentsthecontributionof

theBreit–Wigner termrelativetothe photon-exchangeterm. The quantities

λ

and fZ arefreeparametersofthefit.Theparameters



Z andmZaredeterminedseparatelyfortheC1andtheC2events

from a fitto the_mμ+μ− distributionin the massrange ofthe Z bosonbetween80and120 GeV.Thefitprovidestheeffective val-uesofsuchquantities,thatincludedetectorandresolutioneffects for each set of data. Their valuesare used in Fbkg andare kept

constantinthefit.

Alinearcombinationofthetwofunctionsfortheexpected sig-nal andbackgroundisthenused inan unbinnedlikelihoodfit to thedata:

Ffit

= (

1

−

fbkg

)

Fsig

+

fbkgFbkg

.

(4)

The parametersthat describethesignal aredetermined inthe fitofthesimulatedsignaltoEq.(2),foreachpairofmA andtan

β

values.Subsequently,theyarefixedinFfit,wherethefree

parame-tersarethequantities

λ

, fZ,and fbkg.Thefractionofsignalevents

is defined as fsig

= (

1

−

fbkg

)

. The data are fittedto Ffit in the

mass range from 115to 300 GeV for each point in the mA and

tan

β

parameterspace. Asanexample,thefittothedataofC2at

√

s

=

8 TeV isillustratedinFig. 6,(bottom),assumingasignalwith mA

=

150 GeV andtan

β

=

30.

7. Systematicuncertainties

Thefollowingsourcesofsystematicuncertaintiesaretakeninto account, and the impact ofone standard deviationchange is re-ported in terms of a variation in the nominal signal efficiency definedinSection5.

The limited number of simulated events introduces an un-certainty in the signal selection efficiency that is at most 2.0%. The muon trigger, reconstruction, identification, andisolation ef-ficiencies are determined fromdata using a tag-and-probe tech-nique [38].The uncertainty in the triggerefficiency correction is

Fig. 6. InvariantmassdistributionoftheexpectedsignalformA=150 GeV and

tanβ=30 (top),andanexampleofthefittothedataat√s=8 TeV includingthe samesignalassumption(bottom).Thedistributionrepresentstheexpectednumber ofeventsforanintegratedluminosityof19.3 fb−1_{.Foreachplotthepullofthefit}

asafunctionofthedimuoninvariantmassisshown.

0.5%,whereas1.0%isassignedtothecombinationofuncertainties inmuonreconstruction andidentification, aswell asonisolation efficiencies.

Asystematicuncertaintyinthepileupmultiplicityisevaluated by changing the total cross section for inelastic pp collisions in simulation.Thecorresponding uncertaintyonthesignalefficiency isatmost0.8%inbothcategories.

Theeventfractionsinthetwocategoriesdependontheb tag-gingefficiencyandthemistaggingprobability.The uncertaintyin thebtaggingefficiencyisestimatedby comparingdataand sim-ulatedeventswithsamples ofenriched b quark contentand dif-ferenttopologies,asdescribedinRef.[52].The uncertaintyinthe efficiencyto detectbjetsisabout3.0%.Similarly,theuncertainty inthemistagging rateisabout10%. Theiroverall contributionto theselection efficiencyis weighted by thefraction ofAPandGF eventsthat are expected in each eventcategory, which depends onmAandtan

β

.Thelargestoveralluncertaintyis3.0%forC1,and

0.4%forC2events.

Thejet energyscale uncertaintyis estimatedbysmearing the jetmomentumbya factordependingon pT and

η

ofeachjet, as

described in Ref. [37]. The effecton signal selection efficiencyis 4.0% forevents that belong to the C1 and 0.5% for the C2 cate-gories,at

√

s

=

8 TeV.For

√

s

=

7 TeV thecorrespondingnumbers are3.8% and0.6%.The uncertaintyinthe Emiss

T scaleand

resolu-tionisestimatedthrough comparisonsbetweendataand

simula-Table 3

SourcesofsystematicuncertaintiesforC1andC2eventcategoriesthataffectthe signal efficiencyat √s=8 TeV.They areexpressed interms ofrelative signal selectionefficiency.Whenthesystematicuncertaintyat√s=7 TeV differsfrom

√

s=8 TeV,thecorrespondingvalueisquotedinparenthesis. Source Systematic uncertainty (%)

C1 C2 MC statistics 2.0 2.0 Trigger efficiency 0.5 0.5 Muon efficiency 1.0 1.0 Muon isolation 1.0 1.0 Pileup 0.8 0.8 b tagging 3.0 0.4

Jet energy scale 4.0 (3.8) 0.5 (0.6)

Emiss

T 3.0 (2.0) 3.0 (2.0)

Integrated luminosity 2.6 (2.2) 2.6 (2.2)

PDFs 3.0 3.0

Width correction 1–3 1–5

tion[53,54].Theeffectonthesignalselectionefficiencyis3.0%and 2.0%,thesameforbothcategories,forthesamplewith

√

s

=

8 and 7 TeV,respectively.Theuncertaintyintheintegratedluminosityis 2.6%and2.2%at

√

s

=

8 and7 TeV,respectively[55,56].

UncertaintiesduetothechoiceofPDFsetaffectthesignal effi-ciency, andare studiedusing thePDF4LHC [57] prescription.The renormalization and factorization scales in the calculations and their changes aresummarized inRefs. [16–18].The effecton the signalselectionefficiencyvariesfrom1.0%to3.0%overthemAand

tan

β

parameterspace. Thechoiceof3.0%istakenasthe system-aticuncertainty.

The efficiency is determined for events with generated mass valueswithin awindow ofa factorof3ofthe intrinsicwidthof theHiggsboson,asdescribedinSection5.Thedifferencerelative to the efficiency obtained using a cutoff of a factor of 5 of the intrinsicwidthisassignedasasystematicuncertainty.The uncer-tainty is between1% to 3% forthe C1 and1% to 5% for the C2 categories.

Table 3lists thesystematicuncertainties thataffectthe deter-minationofsignalefficiency.Theimpactofthesesystematic uncer-taintiesontheexclusionlimitsthatwillbepresentedinSection8 is negligible compared to the statistical uncertainty. All the sys-tematicuncertaintiesinTable 3arecorrelatedforthe

√

s

=

7 TeV and8 TeVdata,withtheexceptionoftheuncertaintiesrelatedto thelimitedMCstatisticsandtheintegratedluminosity.

The uncertainties inthe MSSM cross sections depend onmA,

tan

β

,andthescenario,andare providedby theLHCHiggsCross Section Working Group [16–18]. The signal eventsare generated using pythia, assuming the parameters of the mmax_h scenario, as discussed inSection 3.The differentbenchmarksareexpectedto affecttheproductioncrosssection,butnotthekinematic proper-tiesoftheeventsrelatedtoHiggsbosonproductionanddecay.To checkthisassumption,eventsaregeneratedwith pythia usingthe parametersforthemmod_h +,m_hmod−,lightstopandlightstau bench-marks, assuming mA

=

150 GeV and tan

β

=

20. The events are

generatedforboththeGFandtheAPmechanisms,andtheHiggs boson pT andthe EmissT of theevents are comparedat generator

level for the various benchmark scenarios. No significant differ-encesareobservedinthedistributionsofthesequantities.

Sincethenumberofbackgroundeventsisdeterminedthrough a fittothedata,an additionalsystematicuncertaintyarisesfrom the possibility that the background parametrizationmay not ad-equately describe thedata asa functionof thedimuon invariant mass. Amethod similar to that described inRef. [10] is used to evaluatetheeffect,byestimatingtheuncertaintythroughthebias intermsofthenumberofsignal eventsthat arefound when

fit-tingthesignal

+

backgroundmodel(asdescribed inSection6)to pseudo-datagenerated for different alternative background mod-els. Such alternative background parametrizations include Bern-stein polynomials and combinations of Voigtian and exponential functions. Bias estimatesare performed formasspoints between mA

=

115 and300 GeV.ForeachmAvalue,thelargestbiasamong

thetestedfunctionsistakenastheresultinguncertainty.Thebias isimplementedasa floatingadditive contributiontothenumber ofsignalevents,constrainedbyaGaussianprobabilitydensitywith mean of zero and width set to the systematic uncertainty. The width of the Gaussian is the largest systematicuncertainty, and the effectis to increase the expected limit on the presence ofa signalby20%intheregionnearmA

=

120 GeV andbyabout10%

atlargermassvalues.

Inthe massrangebetween115and300 GeV,that isrelevant forthisanalysis, the mass resolutionis estimatedto be between 1.2and4 GeV.Uncertaintiesinthemuonmomentum determina-tion can affect the invariant mass measurement, and have been carefullystudiedin dataandsimulation[38].The dimuon invari-antmassresolutionformassesabovethe Zpeakhasbeen previ-ouslystudied inthesearch fora SMHiggs decayingtoadimuon pair[58].ThemassresolutiondeterminedfromdataattheZmass value is 1 GeV, in excellent agreement withthe prediction from simulation. This value is consistent with the mass resolution of 1.2 GeVthatwe estimatefromsimulationforamassof115 GeV, thatcorresponds tothelower edgeofthe Higgsmassrange con-sideredinthisanalysis.

Theoverallcapabilityoftheanalysistodetectthepresenceofa signalisverifiedbyintroducingahypotheticalsimulatedsignalin the datausing the shape parametrizationdiscussed inSection 6. The average measured number of signal events is found to be within1.3% oftheinjectedsignal fortheC1category, andwithin 4.3%fortheC2category.Thesedifferencesareassignedas system-aticuncertainties.

8. Results

No evidenceofMSSM Higgsbosons productionisobservedin the mass range between 115 and 300 GeV, where the analysis has been performed. Upper limits at 95% confidence level (CL) on theparameter tan

β

are computedusingthe CLs method[59,

60], which is a modified frequentist criterion, andare presented as a function of mA. Systematic uncertainties are incorporated

as nuisance parameters andtreated according to the frequentist paradigm [61]. The results are obtained from a combination of botheventcategoriesandcentre-of-massenergies.Foreachvalue ofmA,the value oftan

β

atwhichthe CLexceeds 95%is chosen

todefinetheexclusionlimitonthatmA.Thisisperformedforall

themA values andthe resultsare shownin Fig. 7.These results

areobtainedwithin themmod_h +scenario.Theobservedupper lim-itsrangefromtan

β

ofabout15inthelow-mAregion,toabove40

atmA

=

300 GeV.Forlarger valuesofmA theuncertaintyonthe

tan

β

upperlimit becomes large,exceeding tan

β

=

50,for which theMSSMcross-sectionpredictionsarenotreliable.

Acomparison withtheresults obtainedforthe mmod_h −,mmax_h , lightstopandlightstauscenariosisalsoperformed.Theexclusion limitscomputedwithintheseotherbenchmarkmodelsareallvery similar. Foranyvalue ofmA,the quantity

tan

β

=

tan

β

_mmod+

h

−

tan

β

scenario representsthedifferenceofthetan

β

valuesatwhich

the95% CL limit isdetermined ifan alternative scenariois used. Fig. 8 showsthequantity

tan

β

asa function ofmA forallthe

testedscenarios. FormostmA values,the 95% CLlimitson tan

β

computedwithinagivenscenariodifferbylessthanoneunitfrom theresultsobtainedwithinthemmod_h + scenario.

Fig. 7. The95%CLupperlimitontanβasafunctionofmA,aftercombiningthedata

fromthetwoeventcategoriesatthetwocentre-of-massenergies(7and8 TeV).The resultsareobtainedintheframeworkofthemmod_h +benchmarkscenario.

Fig. 8. Comparisonofthe95%CLexclusionlimitsontanβobtainedwithinMSSM benchmark models, as a function ofmA. The quantity tanβ=tanβ_mmod+

h −

tanβscenariorepresentsthedifferenceintanβatwhichthe95%CLlimitisobtained

foralternativescenarios.

Limits on the productioncross section times decay branching fraction

σ

B(φ →

μ

+

μ

−

)

for a generic single neutral boson

φ

aredetermined.Inthismodelindependentanalysisnoassumption is made on the cross section, mass, andwidth of the

φ

bosons, which is sought as a single resonance with mass mφ. The anal-ysis isperformed assuming thenarrow widthapproximation, for whichtheintrinsicwidthofthesignalissmallerthanthe invari-ant massresolution.For thispurposethesimulated signal ofthe A boson for the case tan

β

=

10 is used as a template to com-pute thedetectionefficiencyfora generic

φ

boson decayingto a muonpair.Thesingle

φ

bosonisassumedtobeproducedentirely either via the AP or the GFprocess, and the search for a single resonance with massmφ is performed. The 95% CL exclusion on

σ

B(φ →

μ

+

μ

−

)

is determined as a function of mφ, separately for the two production mechanisms. The combination of events belonging to C1 andC2 is shown in Fig. 9, assuming the

φ

bo-son is produced either via the AP or the GF process. Only data collected at

√

s

=

8 TeV are used,asthey providea better sensi-tivity because of the higher luminosity. In addition, since the

φ

production cross section depends on the centre-of-mass energy, a combination with the 7 TeV results would introduce a model

Fig. 9. The95%CLlimitontheproductofthecrosssectionandthedecaybranching fractiontotwomuonsasafunctionofmφ, obtainedfromamodelindependent

analysisofthedata.Theresultsreferto(top)bquarkassociatedand(bottom)gluon fusionproduction,obtainedusingdatacollectedat√s=8 TeV.

dependenceinthedescriptionofthecrosssectionevolutionwith energy.

9. Summary

Asearch has beenperformed forneutralMSSM Higgs bosons decayingto

μ

+

μ

− frompp collisionscollected withtheCMS ex-perimentat

√

s

=

7 and8 TeV,corresponding tointegrated lumi-nositiesof5.1and19.3 fb−1,respectively.Theanalysisissensitive to Higgs boson production via gluon fusion, and via association witha bb quark pair. The results ofthe search, whichhas been performedinthemassrangebetween115and300 GeV,are pre-sentedinthe mmod_h + framework of theMSSM.With noevidence forMSSM Higgs boson production, this analysisexcludes at 95% CL values of tan

β

larger than 40 for Higgs boson masses up to 300 GeV.Comparisonswithmmod_h −,mmax_h ,lightstop,andlightstau scenariosarealsopresented,andofferverysimilarresultsrelative to themmod_h + benchmark. Limits are determined on the product ofthecrosssectionandbranchingfraction

σ

B(φ →

μ

+

μ

−

)

fora genericneutralboson

φ

at

√

s

=

8 TeV, withoutanyassumptions ontheMSSMparameters.Inthiscasethe

φ

bosonisassumedto beproducedeitherinassociationwithabb quarkpairordirectly throughgluonfusion,andsoughtasasingleresonancewithmass mφ.Exclusionlimitsareinthemassregionfrom115to500 GeV. Formφ

=

500 GeV,values

σ

B(φ →

μ

+

μ

−

)

>

4 fb areexcludedat 95%CLforbothproductionmechanisms.Thesearethemost strin-gentresultsinthedimuonchanneltodate.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrative staffsatCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tion and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); F.R.S.- FNRS andFWO(Belgium);CNPq,CAPES,FAPERJ,andFAPESP (Brazil);MES(Bulgaria);CERN;CAS,MOST,andNSFC(China); COL-CIENCIAS(Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER, ERC IUT and ERDF (Estonia); Academy ofFinland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India);IPM(Iran); SFI(Ireland);INFN (Italy); NRF andWCU (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portu-gal);JINR(Dubna);MON,RosAtom,RASandRFBR(Russia);MESTD (Serbia);SEIDIandCPAN(Spain);SwissFundingAgencies (Switzer-land); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thai-land);TUBITAKandTAEK(Turkey);NASUandSFFR(Ukraine);STFC (UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and EPLANET (Eu-ropean Union); the Leventis Foundation; the A. P. Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral Science Policy Office; the Fonds pour la Formation à la Recherchedansl’Industrieetdansl’Agriculture(FRIA-Belgium);the AgentschapvoorInnovatiedoorWetenschapenTechnologie (IWT-Belgium); theMinistry ofEducation, YouthandSports (MEYS) of theCzechRepublic;theCouncilofScienceandIndustrialResearch, India; the HOMING PLUS programme of Foundation for Polish Science, cofinanced from European Union, Regional Development Fund;the CompagniadiSan Paolo(Torino); the Consorzioper la Fisica (Trieste); MIURproject20108T4XTM (Italy);the Thalisand Aristeia programmes cofinanced by EU-ESF andthe Greek NSRF; the National Priorities Research Program by Qatar National Re-search Fund;theRachadapisekSompot FundforPostdoctoral Fel-lowship,ChulalongkornUniversity(Thailand);andtheWelch Foun-dation.

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CMSCollaboration

V. Khachatryan,

A.M. Sirunyan,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

E. Asilar,

T. Bergauer,

J. Brandstetter,

E. Brondolin,

M. Dragicevic,

J. Erö,

M. Flechl,

M. Friedl,

R. Frühwirth

1

,

V.M. Ghete,

C. Hartl,

N. Hörmann,

J. Hrubec,

M. Jeitler

1

,

V. Knünz,

A. König,

M. Krammer

1

,

I. Krätschmer,

D. Liko,

T. Matsushita,

I. Mikulec,

D. Rabady

2

,

B. Rahbaran,

H. Rohringer,

J. Schieck

1

,

R. Schöfbeck,

J. Strauss,

W. Treberer-Treberspurg,

W. Waltenberger,

C.-E. Wulz

1

InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,

N. Shumeiko,

J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt,

T. Cornelis,

E.A. De Wolf,

X. Janssen,

A. Knutsson,

J. Lauwers,

S. Luyckx,

S. Ochesanu,

R. Rougny,

M. Van De Klundert,

H. Van Haevermaet,

P. Van Mechelen,

N. Van Remortel,

A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,

F. Blekman,

J. D’Hondt,

N. Daci,

I. De Bruyn,

K. Deroover,

N. Heracleous,

J. Keaveney,

S. Lowette,

L. Moreels,

A. Olbrechts,

Q. Python,

D. Strom,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

G.P. Van Onsem,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

P. Barria,

C. Caillol,

B. Clerbaux,

G. De Lentdecker,

H. Delannoy,

D. Dobur,

G. Fasanella,

L. Favart,

A.P.R. Gay,

A. Grebenyuk,

T. Lenzi,

A. Léonard,

T. Maerschalk,

A. Mohammadi,

L. Perniè,

A. Randle-conde,

T. Reis,

T. Seva,

L. Thomas,

C. Vander Velde,

P. Vanlaer,

J. Wang,

F. Zenoni,

F. Zhang

3

UniversitéLibredeBruxelles,Bruxelles,Belgium

K. Beernaert,

L. Benucci,

A. Cimmino,

S. Crucy,

A. Fagot,

G. Garcia,

M. Gul,

J. Mccartin,

A.A. Ocampo Rios,

D. Poyraz,

D. Ryckbosch,

S. Salva,

M. Sigamani,

N. Strobbe,

M. Tytgat,

W. Van Driessche,

E. Yazgan,

N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez,

C. Beluffi

4

,

O. Bondu,

G. Bruno,

R. Castello,

A. Caudron,

L. Ceard,

G.G. Da Silveira,

C. Delaere,

D. Favart,

L. Forthomme,

A. Giammanco

5

,

J. Hollar,

A. Jafari,

P. Jez,

M. Komm,

V. Lemaitre,

A. Mertens,

C. Nuttens,

L. Perrini,

A. Pin,

K. Piotrzkowski,

A. Popov

6

,

L. Quertenmont,

M. Selvaggi,

M. Vidal Marono

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

N. Beliy,

T. Caebergs,

G.H. Hammad

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior,

G.A. Alves,

L. Brito,

M. Correa Martins Junior,

T. Dos Reis Martins,

C. Hensel,

C. Mora Herrera,

A. Moraes,

M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas,

W. Carvalho,

J. Chinellato

7

,

A. Custódio,

E.M. Da Costa,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

L.M. Huertas Guativa,

H. Malbouisson,

D. Matos Figueiredo,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

A. Santoro,

A. Sznajder,

E.J. Tonelli Manganote

7

,

A. Vilela Pereira

S. Ahuja,

C.A. Bernardes

b

,

A. De Souza Santos,

S. Dogra

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

P.G. Mercadante

b

,

C.S. Moon

a

,

8

,

S.F. Novaes

a

,

Sandra S. Padula

a

,

D. Romero Abad,

J.C. Ruiz Vargas

a_{UniversidadeEstadualPaulista,SãoPaulo,Brazil} b_{UniversidadeFederaldoABC,SãoPaulo,Brazil}

A. Aleksandrov,

V. Genchev

2

,

R. Hadjiiska,

P. Iaydjiev,

A. Marinov,

S. Piperov,

M. Rodozov,

S. Stoykova,

G. Sultanov,

M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov,

I. Glushkov,

L. Litov,

B. Pavlov,

P. Petkov

UniversityofSofia,Sofia,Bulgaria

M. Ahmad,

J.G. Bian,

G.M. Chen,

H.S. Chen,

M. Chen,

T. Cheng,

R. Du,

C.H. Jiang,

R. Plestina

9

,

F. Romeo,

S.M. Shaheen,

J. Tao,

C. Wang,

Z. Wang,

H. Zhang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee,

Y. Ban,

Q. Li,

S. Liu,

Y. Mao,

S.J. Qian,

D. Wang,

Z. Xu,

W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,

A. Cabrera,

L.F. Chaparro Sierra,

C. Florez,

J.P. Gomez,

B. Gomez Moreno,

J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic,

D. Lelas,

D. Polic,

I. Puljak

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

K. Kadija,

J. Luetic,

L. Sudic

InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,

M. Finger

10

,

M. Finger Jr.

10

CharlesUniversity,Prague,CzechRepublic

R. Aly

11

,

S. Aly

11

,

E. El-khateeb

12

,

T. Elkafrawy

12

,

A. Lotfy

13

,

A. Mohamed

14

,

A. Radi

15

,

12

_,

E. Salama

12

,

15

,

A. Sayed

12

,

15

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

B. Calpas,

M. Kadastik,

M. Murumaa,

M. Raidal,

A. Tiko,

C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,

V. Karimäki,

R. Kinnunen,

T. Lampén,

K. Lassila-Perini,

S. Lehti,

T. Lindén,

P. Luukka,

T. Mäenpää,

J. Pekkanen,

T. Peltola,

E. Tuominen,

J. Tuominiemi,

E. Tuovinen,

L. Wendland

J. Talvitie,

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

B. Fabbro,

J.L. Faure,

C. Favaro,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

E. Locci,

M. Machet,

J. Malcles,

J. Rander,

A. Rosowsky,

M. Titov,

A. Zghiche

DSM/IRFU,CEA/Saclay,Gif-sur-Yvette,France

S. Baffioni,

F. Beaudette,

P. Busson,

L. Cadamuro,

E. Chapon,

C. Charlot,

T. Dahms,

O. Davignon,

N. Filipovic,

A. Florent,

R. Granier de Cassagnac,

S. Lisniak,

L. Mastrolorenzo,

P. Miné,

I.N. Naranjo,

M. Nguyen,

C. Ochando,

G. Ortona,

P. Paganini,

S. Regnard,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

T. Strebler,

Y. Yilmaz,

A. Zabi

LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France

J.-L. Agram

16

,

J. Andrea,

A. Aubin,

D. Bloch,

J.-M. Brom,

M. Buttignol,

E.C. Chabert,

N. Chanon,

C. Collard,

E. Conte

16

,

J.-C. Fontaine

16

,

D. Gelé,

U. Goerlach,

C. Goetzmann,

A.-C. Le Bihan,

J.A. Merlin

2

,

K. Skovpen,

P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,

C. Bernet

9

,

G. Boudoul,

E. Bouvier,

S. Brochet,

C.A. Carrillo Montoya,

J. Chasserat,

R. Chierici,

D. Contardo,

B. Courbon,

P. Depasse,

H. El Mamouni,

J. Fan,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

I.B. Laktineh,

M. Lethuillier,

L. Mirabito,

A.L. Pequegnot,

S. Perries,

J.D. Ruiz Alvarez,

D. Sabes,

L. Sgandurra,

V. Sordini,

M. Vander Donckt,

P. Verdier,

S. Viret,

H. Xiao

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

T. Toriashvili

17

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze

10

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,

S. Beranek,

M. Edelhoff,

L. Feld,

A. Heister,

M.K. Kiesel,

K. Klein,

M. Lipinski,

A. Ostapchuk,

M. Preuten,

F. Raupach,

J. Sammet,

S. Schael,

J.F. Schulte,

T. Verlage,

H. Weber,

B. Wittmer,

V. Zhukov

6

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

M. Ata,

M. Brodski,

E. Dietz-Laursonn,

D. Duchardt,

M. Endres,

M. Erdmann,

S. Erdweg,

T. Esch,

R. Fischer,

A. Güth,

T. Hebbeker,

C. Heidemann,

K. Hoepfner,

D. Klingebiel,

S. Knutzen,

P. Kreuzer,

M. Merschmeyer,

A. Meyer,

P. Millet,

M. Olschewski,

K. Padeken,

P. Papacz,

T. Pook,

M. Radziej,

H. Reithler,

M. Rieger,

F. Scheuch,

L. Sonnenschein,

D. Teyssier,

S. Thüer

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov,

Y. Erdogan,

G. Flügge,

H. Geenen,

M. Geisler,

W. Haj Ahmad,

F. Hoehle,

B. Kargoll,

T. Kress,

Y. Kuessel,

A. Künsken,

J. Lingemann

2

,

A. Nehrkorn,

A. Nowack,

I.M. Nugent,

C. Pistone,

O. Pooth,

A. Stahl

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,

I. Asin,

N. Bartosik,

O. Behnke,

U. Behrens,

A.J. Bell,

K. Borras,

A. Burgmeier,

A. Cakir,

L. Calligaris,

A. Campbell,

S. Choudhury,

F. Costanza,

C. Diez Pardos,

G. Dolinska,

S. Dooling,

T. Dorland,